WEC Energy Group FERC Part 12D Comprehensive Assessments

Challenges

WEC Energy Group (WEC) owns and operates 30 hydroelectric dams in northeast Wisconsin and the Upper Peninsula of Michigan. The Federal Energy Regulatory Commission (FERC) requires that an Independent Consultant (IC) team inspect and evaluate licensed hydroelectric facilities on a routine basis. A Comprehensive Assessment (CA) is typically required every 10 years and requires a semi-quantitative (Level 2) risk analysis (L2RA). Approximately half of historical dam failures have been caused by internal erosion, and therefore a strong understanding of geotechnical and geological engineering is important for assessing seepage-related potential failure modes.

Solution

RJH was retained as part of an IC team to perform FERC Part 12 CAs at seven WEC dams.  RJH’s role on the team was to provide geotechnical and geologic subject matter expert services.  A CA provides a thorough evaluation of a project’s overall dam safety by reviewing its design and construction, current condition and performance, data and records, dam safety programs, and potential failure modes.

RJH’s role for the CAs included the following primary tasks:

• Reviewed the Supporting Technical Information Document, previous Part 12D reports, FERC inspection reports and correspondence, design drawings and calculations, construction records, geologic/geotechnical information, instrumentation data, and other records.
• Developed interpretations of subsurface conditions.
• Identified site-specific seismic loads and performed screening-level geotechnical calculations (seepage gradients, liquefaction triggering susceptibility, etc.) to support risk assessments.
• Prepared geotechnical and geologic sections of the Pre-Inspection Preparation Report to demonstrate to FERC that the IC team is familiar with the project and is prepared to perform the CA.
• Performed a detailed site inspection of the dam, spillway, outlet works, gates, penstocks/water conveyance structures, powerhouse, and other safety-related structures.
• Participated in a Potential Failure Modes Analysis workshop to brainstorm, screen, and develop potential failure modes, focus investigations, monitoring, engineering evaluations, and risk-reduction activities.
• Participated in an L2RA workshop to estimate risk (annual probability and consequences) for significant potential failure modes and identify potential risk-reduction measures.
• Prepared a Comprehensive Assessment Report.